JP2011133823A - Rotary driving device, image forming apparatus, and method for controlling the rotary driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively perform accurate rotational speed control of a motor by improving speed resolution of the motor determined according to frequency of a clock signal without replacing a rotary driving device with an expensive device coping with a high-speed clock signal. <P>SOLUTION: The rotary driving device includes: the motor for rotating a rotating body; a motor controller; a speed detection part that outputs a pulse every time the rotating body or a driven rotating body following the rotating body rotates by a fixed angle; a count part that measures the cycle of the pulse output by the speed detection part by counting the clock signal; and an arithmetic operation part that obtains a difference between a value obtained by multiplying a command value to be counted by the count part as the cycle of the pulse by a predetermined value and a value obtained by multiplying the counted value counted actually by the count part by the predetermined value, integrates the obtained difference, and outputs an acceleration/deceleration command to the motor controller based on a calculated value obtained by dividing the integrated value by the predetermined value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotation drive device that rotates a rotating body using a motor, and an image forming apparatus such as a multifunction machine, a copier, a printer, and a facsimile machine including the rotation drive device.

  For example, there is an image forming apparatus that forms toner images of a plurality of colors and performs printing by superimposing them (for example, a tandem type). In such an image forming apparatus, a photosensitive drum and an intermediate transfer belt are provided and rotated by a motor. In order to superimpose the toner images of the respective colors without deviation, it is necessary to accurately control the rotational speed of the motor that rotates the photosensitive drum and the intermediate transfer belt.

  For example, Patent Document 1 includes a plurality of image forming units and an endless belt that is stretched between a driving roller and a driven roller and receives image transfer directly or indirectly from each image forming unit. A speed increasing mechanism including at least one rotating body is provided, a rotation detecting means is provided on the increased output shaft, a common multiple cycle of the rotating periods of all the rotating bodies constituting the speed increasing mechanism is Tx, and the endless belt is A multi-transfer type color image forming apparatus is described in which a speed increasing mechanism is configured to satisfy Tx: Tu = 1: n, where Tu is the time required to move between image forming units and n is a natural number. ing. With this configuration, without using a high-precision and high-resolution encoder, it is possible to detect a rotational fluctuation of the photosensitive member or the belt and obtain a multiple transfer type color image forming apparatus with little color misregistration (Patent Document 1: Claim). 1, paragraph [0031] etc.).

JP 2005-003920 A

  For example, when detecting the rotational speed of the photosensitive drum or the intermediate transfer belt, for example, a clock signal may be counted to measure time. For example, in the speed control of the intermediate transfer belt, a rotary encoder is provided on a roller for rotating the intermediate transfer belt, and the time between pulses generated by the rotary encoder is counted by counting a clock signal. May detect the rotation speed. The controller that controls the rotation of the intermediate transfer belt may control the rotation speed of the motor so that the period of the pulses generated by the rotary encoder is constant (so that the count value of the clock signal is constant). is there.

  Therefore, a high-speed clock signal is used to increase the accuracy in the detection of the rotation speed and the speed control. However, if the clock signal is increased in order to increase the speed resolution, a high-speed device or the like corresponding to the high-speed clock signal is required. In general, the faster the device, the more expensive it is, and there is a problem that if the speed of the clock signal is increased unnecessarily, the manufacturing cost of the rotary drive device increases.

  In the invention described in Patent Document 1, a pair of pulley trains (speed increasing pulleys 11 and 12) are provided as a speed change mechanism, and a rotary as rotation detecting means is provided on the speed increasing pulley 12 shaft that is an output shaft of the speed change mechanism. An encoder 13 is installed, and high resolution in speed detection is to be realized at low cost by a combination of a low resolution encoder and a speed increasing mechanism (see Patent Document 1: Paragraph [0046] and the like). On the other hand, in Patent Document 1, the pulse generator 112 outputs a motor drive pulse train, and the driver unit 113 drives the stepping motor 114 according to the motor drive pulse train (see Patent Document 1: Paragraph [0108], FIG. 14, etc.). ) To solve the problem that high speed clock signal and expensive device are required to set the motor speed at high resolution in response to high resolution speed detection, which increases the manufacturing cost of the rotary drive device. I can't.

  In view of the above problems, the present invention increases the speed resolution of a motor determined by the frequency of the clock signal without replacing it with an expensive device corresponding to a high-speed clock signal, and provides a high-precision motor rotational speed control at a low cost. The task is to do.

  In order to achieve the above object, a rotary drive device according to claim 1 includes a motor for rotating a rotating body, a motor control unit for controlling the rotation of the motor, and the rotating body or driven by the rotating body. A speed detection unit that outputs a pulse each time the driven rotating body rotates by a certain angle, a pulse period generated by the speed detection unit, a count unit that counts a clock signal and counts, and the count as the pulse period A difference between a value obtained by multiplying the command value to be counted by the predetermined value by a predetermined value and a value obtained by multiplying the count value actually counted by the counting unit by the predetermined value is obtained, and the obtained differences are integrated and integrated. Based on a calculated value obtained by dividing the value by the predetermined value, an arithmetic unit that outputs an acceleration / deceleration command to the motor control unit is provided.

  According to this configuration, when the acceleration / deceleration command is output from the calculation unit based on the difference between the command value and the count value, the command value and the count value are respectively multiplied by the predetermined value, and then the difference is obtained and the difference is integrated. The calculated value is obtained by dividing the integrated value by a predetermined value. In this way, the value obtained by multiplying the difference once multiplied by the predetermined value is divided by the predetermined value. As a result, a value that is originally less than the speed resolution and is not given as a command value, or a value that has been truncated even if given, is multiplied by a predetermined value and becomes larger. Can be given as. In addition, the values that were originally rounded down below the speed resolution are sequentially integrated and reflected in the acceleration / deceleration command by a carry. Therefore, the speed resolution can be increased without increasing the clock signal speed, and the rotation speed of the motor or the rotating body can be controlled with high accuracy. Moreover, since it is not necessary to increase the clock signal speed, the manufacturing cost of the rotary drive device does not increase, which is advantageous in terms of cost.

  The invention according to claim 2 is the invention according to claim 1, wherein the predetermined value is an integer.

  According to this configuration, the predetermined value is an integer. Thereby, the value below the speed resolution given as the command value is surely increased.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the calculation unit gives an instruction to the motor control unit that the motor should rotate faster as the calculated value is larger. If the calculated value is a negative value, an instruction not to accelerate the motor is output to the motor control unit.

  For example, when the rotation speed of the motor is slower than the desired rotation speed, such as at the beginning of rotating the motor, the difference between the command value and the count value increases. Therefore, according to this configuration, the calculation unit outputs an instruction to the motor control unit that the motor should rotate faster as the calculated value increases. If the calculated value is a negative value, an instruction not to accelerate the motor is output to the motor control unit. Thereby, a motor and a rotary body are maintained with high precision at the rotational speed at the speed according to the command value.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus including the rotation driving device according to any one of the first to third aspects.

  According to this configuration, since the rotation driving device in which the rotation speed of the rotating body is controlled with high accuracy is included, the image can be formed without deviation. Accordingly, it is possible to provide an image forming apparatus with high image quality to be formed.

  The invention according to claim 5 includes the image forming unit for forming a toner image of a plurality of colors and an intermediate transfer belt on which the formed toner images of each color are superimposed and transferred. A speed detection unit is attached to a roller that stretches the intermediate transfer belt, and the speed detection unit is a rotary encoder that is attached to the roller and outputs a pulse every time the roller rotates by a certain angle.

  According to this configuration, the speed detector is attached to the roller that stretches the intermediate transfer belt, and the rotational speed of the intermediate transfer belt is controlled with high accuracy, so that the toner images can be superimposed without deviation as intended. .

  According to a sixth aspect of the present invention, there is provided a method for controlling a rotary drive device comprising: a motor for rotating a rotating body; a motor control unit for controlling the rotation of the motor; and the driven body driven by the rotating body or the rotating body. A rotation including a speed detection unit that outputs a pulse each time the rotating body rotates by a certain angle, a counting unit that counts a clock signal by counting a cycle of the pulse generated by the speed detection unit, and a calculation unit that performs a calculation. A control method for a driving device, wherein the calculation unit multiplies a command value to be counted by the counting unit as a cycle of the pulse by a predetermined value, and the count value actually counted by the counting unit is the predetermined value. The difference between a value obtained by multiplying the command value by a predetermined value and a value obtained by multiplying the count value by the predetermined value is obtained, and the obtained difference is integrated and obtained by dividing the integrated value by the predetermined value. Based on the calculated value Can, it was decided to output the deceleration command to the motor controller.

  This configuration captures the invention according to claim 1 as a method, and the same effect as that of the invention according to claim 1 can be obtained.

  Originally, in order to control the motor with a speed resolution that exceeds the speed resolution of the motor determined by the frequency of the clock signal, it is necessary to increase the speed of the clock signal. However, according to the present invention, it is possible to provide a rotary drive device that can increase the speed resolution and control the rotational speed of the motor with high accuracy at low cost without replacing it with an expensive device corresponding to a high-speed clock signal.

1 is a cross-sectional view illustrating a schematic configuration of a printer according to an embodiment. It is an expanded sectional view of each image forming part concerning an embodiment. FIG. 3 is a block diagram illustrating an example of a hardware configuration of a printer according to an embodiment. It is a block diagram which shows an example of the hardware constitutions of the rotational drive apparatus of embodiment. It is a timing chart for demonstrating the outline | summary of the rotational speed control of the motor in the rotational drive apparatus which concerns on embodiment. (A) is an operation | movement flowchart which shows an example of the calculation process in the conventional CPU, (b) is a timing chart for demonstrating an example of the limit of the conventional speed resolution. It is a calculation flowchart which shows an example of the calculation process in CPU which concerns on embodiment. 6 is a flowchart illustrating an example of a flow of rotational speed control of the intermediate transfer belt according to the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. The present invention can be applied to other image forming apparatuses such as a multifunction machine, a copier, and a FAX apparatus. However, in the present description, an electrophotographic tandem type color printer 200 including the rotation driving device 100 (image forming apparatus). Will be described as an example. However, each element such as the configuration and arrangement described in the present embodiment does not limit the scope of the invention and is merely an illustrative example.

(Schematic configuration of image forming apparatus)
First, an outline of a printer 200 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view illustrating a schematic configuration of a printer 200 according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of each image forming unit 3 according to the embodiment of the present invention. As shown in FIG. 1, the printer 200 according to the present embodiment includes a sheet feeding unit 1, a conveyance path 2, an image forming unit 3, an intermediate transfer unit 4, a fixing unit 5, and the like in the main body.

  For example, the sheet feeding unit 1 stores various sheets such as copy sheets, OHP sheets, and label sheets, and sends them to the conveyance path 2 by a sheet feeding roller 11 that is rotated by a driving mechanism (not shown) such as a motor. The conveyance path 2 conveys the sheet in the printer 200 and guides the sheet supplied from the sheet feeding unit 1 to the discharge tray 21 through the intermediate transfer unit 4 and the fixing unit 5. The conveyance path 2 is provided with a pair of conveyance rollers 22, a guide 23, and a registration roller pair 24 that waits for the conveyed sheet in front of the intermediate transfer unit 4 and sends it in time.

  As shown in FIGS. 1 and 2, the printer 200 has an image forming unit 3 as a part for forming a toner image based on image data of an image to be formed. The image forming unit 3 includes image forming units 30 for four colors. Specifically, the printer 200 forms a magenta image, an image forming unit 30Bk that forms a black image, an image forming unit 30Y that forms a yellow image, an image forming unit 30C that forms a cyan image, and the like. An image forming unit 30M and an exposure device 33 are provided.

  Here, the image forming units 30Bk to 30M will be described in detail with reference to FIG. The image forming units 30Bk to 30M have basically the same configuration except that the color of the toner image to be formed is different. Therefore, in the following description, the symbols Bk, Y, C, and M of each image forming unit 30 are omitted unless specifically described.

  Each photosensitive drum 31 (corresponding to a rotating body) carries a toner image on its peripheral surface, has a photosensitive layer on its outer peripheral surface, and is driven to rotate at a predetermined process speed by a driving device (not shown). Each charging device 32 charges the photosensitive drum 31 at a constant potential. An exposure device 33 below the image forming unit 3 converts the input color-separated image signal into an optical signal, outputs a laser beam (shown by a broken line) that is the converted optical signal, and after charging The photosensitive drum 31 is scanned and exposed to form an electrostatic latent image. Each developing device 34 stores a developer of a corresponding color. Each developing device 34 supplies toner to the electrostatic latent image on the photosensitive drum 31 and develops it. Each cleaning device 35 cleans the photosensitive drum 31.

  Returning to FIG. 1, the intermediate transfer unit 4 receives the primary transfer of the toner image from the photosensitive drum 31 and performs the secondary transfer on the sheet. The intermediate transfer unit 4 includes primary transfer rollers 40Bk to 40M, an intermediate transfer belt 41 (corresponding to a rotating body), a driving roller 42, a plurality of driven rollers 43a to 43h, a secondary transfer roller 44, a belt cleaning device 45, and the like. Consists of. Each primary transfer roller 40Bk to 40M sandwiches the corresponding photosensitive drum 31 and endless intermediate transfer belt 41. A transfer voltage is applied to each of the primary transfer rollers 40Bk to 40M, and the toner image is transferred to the intermediate transfer belt 41.

  The intermediate transfer belt 41 is stretched around a driving roller 42 and the like, and rotates around the driving roller 42 connected to a driving mechanism (not shown) such as a belt motor 4M. The driving roller 42 sandwiches the intermediate transfer belt 41 with the secondary transfer roller 44. The toner images (black, yellow, cyan, and magenta colors) formed by the image forming units 30 are sequentially superimposed and superimposed on the intermediate transfer belt 41, and then a predetermined voltage is applied. The image is transferred onto the sheet by the secondary transfer roller 44.

  The fixing unit 5 is disposed downstream of the secondary transfer unit in the transfer material conveyance direction, and fixes the toner image secondarily transferred to the sheet by heating and pressing. The fixing unit 5 is mainly composed of a fixing roller 51 with a built-in heat source and a pressure roller 52 pressed against the fixing roller 51, and forms a nip. The sheet on which the toner image has been transferred is heated and pressurized as it passes through the nip, and as a result, the toner image is fixed on the sheet. The fixed sheet is discharged to the discharge tray 21 and the image forming process is completed.

(Hardware configuration of printer 200)
Next, a hardware configuration of the printer 200 according to the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram illustrating an example of a hardware configuration of the printer 200 according to the embodiment of the present invention.

  As shown in FIG. 3, the printer 200 according to the present embodiment includes a control unit 6 inside. The control unit 6 controls each unit of the printer 200. For example, the control unit 6 includes a CPU 7 (corresponding to a calculation unit), an image processing unit 61, and the like. The control unit 6 is for each function, such as a main control unit that performs overall control and image processing, an engine control unit that controls printing by performing ON / OFF of a motor that rotates an image forming and various rotating bodies, and the like. Multiple types may be provided by dividing. In addition, in this description, the form which put these control parts together is shown and demonstrated.

  The control unit 6 is connected to the storage unit 62. The CPU 7 in the control unit 6 is a central processing unit, and controls and performs each unit of the printer 200 based on a control program stored in the storage unit 62 and developed. The storage unit 62 is configured by a combination of nonvolatile and volatile storage devices such as ROM, RAM, flash ROM, and HDD. For example, the storage unit 62 stores a control program, control data, and the like for the printer 200.

  The control unit 6 also has an I / F that communicates via a network or cable with a computer 300 (for example, a personal computer) that is a transmission source of print data including image data to be printed and setting data for printing. Unit 63 (interface unit) is connected.

  The image processing unit 61 performs various image processing such as enlargement, reduction, density conversion, data format conversion, and the like on the image data from the computer 300 according to the setting. Then, the image processing unit 61 sends the image data after the image processing to the exposure device 33. The exposure device 33 receives this image data, performs scanning and exposure, and forms an electrostatic latent image on the photosensitive drum 31.

  The control unit 6 is connected to the sheet feeding unit 1, the conveyance path 2, the image forming unit 3, the exposure device 33, the intermediate transfer unit 4, the fixing unit 5, the operation panel 64, and the like. Based on the above, the operation of each unit is controlled so that image formation is appropriately performed. The operation panel 64 is provided, for example, at the upper front of the printer 200, has a liquid crystal screen, and displays various setting information, warnings, and the like.

(Hardware configuration of rotation drive device 100)
Next, an example of the rotary drive device 100 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 4. FIG. 4 is a block diagram illustrating an example of a hardware configuration of the rotary drive device 100 according to the embodiment of the present invention.

  The rotation drive device 100 of the present embodiment is provided, for example, for rotating a rotating body that requires highly accurate rotation speed control. For example, a toner image of each color is superimposed on the intermediate transfer belt 41. If there is a large fluctuation in the rotation speed of the intermediate transfer belt 41, the toner images on the intermediate transfer belt 41 are misaligned, and the image quality can be degraded. As described above, the intermediate transfer belt 41 needs to be rotated while maintaining a predetermined speed with high accuracy even when the load varies. Therefore, in the printer 200 of the present embodiment, the intermediate transfer belt 41 is rotated using the rotation driving device 100 according to the present invention.

  The rotation driving device 100 for rotating the intermediate transfer belt 41 includes, for example, a belt motor 4M (corresponding to a motor), a driver 8 (corresponding to a motor control unit), a speed detection unit 9, a control unit 6, and the like.

  The belt motor 4M is, for example, a brushless DC motor. The belt motor 4M rotates the driving roller 42 in the intermediate transfer unit 4 using a gear or the like. By rotating the driving roller 42, the intermediate transfer belt 41 stretched by a plurality of rollers including the driving roller 42 is rotated.

  The driver 8 is configured as an IC, for example, and controls the ON / OFF and rotation speed of the belt motor 4M based on an instruction from the control unit 6. For example, the driver 8 includes a PWM circuit corresponding to the number of phases of the motor (for example, if the brushless DC motor has three phases, a three-phase output), and the duty and frequency of a signal given to the motor based on an instruction from the control unit 6 Etc. are controlled to control the rotation speed of the motor.

  The speed detector 9 is for detecting the rotational speed of the intermediate transfer belt 41, and is provided between the drive roller 42 and the primary transfer roller 40Bk, for example, and attached to a driven roller 43a adjacent to the drive roller 42. . In addition, you may attach to the other driven rollers 43a-43h.

  The speed detector 9 is a rotary encoder, for example, and emits a pulse every time the driven roller 43a rotates by a certain angle. For example, the speed detector 9 outputs a pulse every time the driven roller 43a rotates once. The speed detection unit 9 may be, for example, every half rotation of the driven roller 43a, and how much the driven roller 43a rotates may be set as appropriate as to whether the speed detection unit 9 emits a pulse.

  The output of the speed detector 9 is connected to the CPU 7 of the controller 6. The control unit 6 includes an element in the control unit 6 and a clock signal generation unit 71 for driving the CPU. The clock signal generation unit 71 may be provided outside the control unit 6 as long as it can supply a clock signal to the CPU 7 and the like. The clock signal generation unit 71 includes, for example, a vibrator, a multiplication circuit, and the like, and generates a clock signal for driving the CPU.

  The CPU 7 is provided with a count unit 72 (counter) that counts clock signals. For example, the count unit 72 counts the clock signal from when a pulse is generated from the speed detection unit 9 until the next pulse is generated in order to measure the period of the pulse generated by the speed detection unit 9. For example, the slower the rotation of the intermediate transfer belt 41, the greater the count value of the count unit 72. On the other hand, the faster the rotation of the intermediate transfer belt 41, the smaller the count value. Based on the count value of the count unit 72, the control unit 6 can grasp the speed of the intermediate transfer belt 41.

(Motor rotation speed control)
Next, based on FIG. 5, the outline of the rotational speed control of the motor in the rotation drive device 100 according to the embodiment of the present invention will be described. FIG. 5 is a timing chart for explaining the outline of the rotational speed control of the motor in the rotary drive device 100 according to the embodiment of the present invention.

  As described above, the count unit 72 of the present embodiment counts the clock signal. Then, the count unit 72 measures the cycle T1 of the pulse output from the speed detection unit 9. For example, when the speed detection unit 9 outputs a pulse that changes from Low to High (may be High to Low), for example, the counting unit 72 counts by looking at the rising edge (or falling edge) of the clock signal. In other words, the count unit 72 measures the time from the rising edge of the pulse output by the speed detection unit 9 to the next rising edge, or from the falling edge to the falling edge.

  Then, the CPU 7 of the control unit 6 controls the rotation speed of the belt motor 4M so that the count value of the count unit 72 becomes a constant value during image formation. If the count value becomes a constant value, the intermediate transfer belt 41 is rotating at a constant speed. For example, the speed detector 9 outputs a pulse once per rotation of the driven roller 43a, and the desired rotation speed of the intermediate transfer belt 41 (the movement speed of the surface of the intermediate transfer belt 41) matches the peripheral speed of the driven roller 43a. In this case, the constant value in the count value is the number of clocks corresponding to the time obtained by dividing the circumferential length of the driven roller 43a by the desired rotation speed of the intermediate transfer belt 41. Note that a constant value may be obtained in consideration of slipping or the like.

  Although details will be described later, in the present invention, a difference between a command value (the above-described constant value) as a count value to be counted by the count unit 72 and a count value actually counted by the count unit 72 is obtained. Whether or not to accelerate the belt motor 4M is determined by the magnitude of the difference value. For example, if the difference obtained by subtracting the count value from the command value is a positive value, the number of clocks counted by the counting unit 72 is smaller than the ideal count value, and therefore the rotational speed of the intermediate transfer belt 41 is set to a desired speed. It will be slower. Therefore, the CPU 7 gives an instruction to the driver 8 to accelerate the belt motor 4M. As a result, the rotation speed of the belt motor 4M increases and the rotation speed of the intermediate transfer belt 41 also increases.

  On the other hand, for example, if the difference obtained by subtracting the count value from the command value is a negative value, the number of clocks counted by the count unit 72 is larger than the ideal count value, so the rotational speed of the intermediate transfer belt 41 is desired. Will be faster than. Therefore, for example, the CPU 7 gives an instruction to the driver 8 not to accelerate the belt motor 4M. As a result, the belt motor 4M tries to continue to rotate due to inertia, but the rotational speed gradually decreases due to the load.

(Speed resolution)
Next, an example of arithmetic processing and speed resolution in the conventional CPU 7 will be described with reference to FIG. FIG. 6A is a calculation flow chart showing an example of calculation processing in the conventional CPU 7, and FIG. 6B is a timing chart for explaining an example of the limit of the conventional speed resolution.

  First, X and Y shown in FIG. 6 will be described. X in FIG. 6 is a command value. Specifically, the command value is a count value to be counted by the counting unit 72 in the cycle T1 of the pulse generated by the speed detection unit 9 (the above-described constant value). In other words, the command value X means the number of clocks that the counting unit 72 should count. On the other hand, Y is a count value between pulses that the count unit 72 actually outputs from the speed detection unit 9.

  Then, the difference between the command value X and the count value Y is taken and integrated. Each time the command value X and the count value Y are input and integrated, the CPU 7 gives an acceleration / deceleration command to the driver 8.

  In such a conventional arithmetic processing, the command value X and the count value Y mean the number of clocks, so that the belt motor 4M is speed controlled in units of clocks. In other words, the rotation of the belt motor 4M cannot be controlled in units smaller than one clock, and the rotation speed of the belt motor 4M cannot be controlled in a time shorter than the cycle of the clock signal. Therefore, the speed resolution of the belt motor 4M is determined by the frequency of the clock signal.

  This point will be described with reference to FIG. In FIG. 6 (b), as indicated by the broken line interval T2, even if the command value X is to be given in units of less than 1 clock (for example, 0.25 clock, 0.125 clock, etc.) In the conventional arithmetic processing, the command value X is an integer of 1 or more. Therefore, the command value X is a section from the start point of the section T2 to a section T3 from the position closest to the dashed section T2 (position indicated by an upward arrow in FIG. 6B) to the next closest clock. Only given as T4. Further, as shown in FIG. 6A, for example, it is meaningless to add a value of 0.125 less than one clock as the command value to the command value X and take a difference from the count value Y. , 0.125 is rounded down.

  Thus, in the arithmetic processing in the conventional rotational speed control of the belt motor 4M, the speed resolution is determined by the frequency (cycle) of the clock signal. Therefore, in order to increase the speed resolution in the rotational speed control of the belt motor 4M, the frequency of the clock signal is increased (the period is shortened). However, for example, if the speed resolution is increased to the time unit of 0.125 clock in one clock of the current clock signal, the clock having a frequency eight times (1 ÷ 0.125 = 8) the current clock signal. A signal is required.

  In general, the devices in the rotary drive device 100 such as the CPU 7 and the driver 8 are more expensive with a high-speed clock. If the speed resolution is high, it is preferable because the speed control of the intermediate transfer belt 41 can be performed with high accuracy. However, in the conventional arithmetic processing, the manufacturing cost of the rotary drive device 100 and the image forming apparatus increases. Therefore, the present invention increases the speed resolution without increasing the frequency of the clock signal of the CPU 7 or the like from the current level. This point will be described below.

(Calculation processing)
Next, an example of arithmetic processing in the CPU 7 according to the embodiment of the present invention will be described based on FIG. FIG. 7 is a calculation flowchart showing an example of calculation processing in the CPU 7 according to the embodiment of the present invention.

  First, X and Y in the arithmetic processing shown in FIG. 7 are command values in the same manner as described in FIG. Y is a count value between the pulses actually output by the speed detector 9 by the count unit 72. X ′ is a command value including a value after the decimal point, and is conventionally a value that has been truncated even if given as a command value as less than one clock. Note that the data such as the command value X and the command value X ′ is stored in, for example, the storage unit 62 and appropriately read out.

  In the arithmetic processing according to the present invention, the command value X, the count value Y, and the command value X ′ are each multiplied by n (multiplied by a predetermined value n). The predetermined value n can be an integer, for example. That is, the predetermined value n is an integer. The predetermined value n may be a number that makes the minimum value at least one of the command values X 'that can be input. For example, as shown in FIG. 7, if the minimum value among the values given as the command value X ′ is 0.125, for example, n = 8. As a result, the command value X ′ is not rounded down, added to the difference between the command value X and the count value Y, and integrated.

  On the other hand, the command value X and the count value Y are multiplied by n, and the accumulated value cannot be used as an instruction to the driver 8. Therefore, an operation for dividing the integrated value by 1 / n (an operation for dividing by the predetermined value n) is performed. An addition / subtraction command is given from the CPU 7 to the driver 8 based on a value obtained by multiplying the integrated value by 1 / n.

  Then, the value corresponding to the command value X ′ may be integrated to be a value of 1 or more when 1 / n. In other words, conventionally rounded down values are integrated and carry is generated, which can affect the rotational speed of the belt motor 4M.

(Flow of rotational speed control)
Next, an example of the flow of rotational speed control of the intermediate transfer belt 41 according to the embodiment of the present invention will be described based on FIG. FIG. 8 is a flowchart showing an example of the flow of rotational speed control of the intermediate transfer belt 41 according to the embodiment of the present invention.

  First, the start of FIG. 8 is, for example, when image data from the computer 300 is input to the printer 200 and printing is started or when the intermediate transfer belt 41 starts to rotate, such as during inspection.

  Next, the CPU 7 multiplies the pulse count value Y, the command value X, and the command value X ′ from the speed detector 9 by n (step # 1). Then, the CPU 7 adds the command value X and the command value X ′ and subtracts the count value Y to obtain the command value X and the difference between the command value X ′ and the count value Y (step # 2).

  For example, when the intermediate transfer belt 41 is initially rotated, the count value Y is small, so the difference value is large. Therefore, for example, the CPU 7 issues an acceleration command to rotate the belt motor 4M faster as the difference value is larger. Then, as the intermediate transfer belt 41 is accelerated and approaches the speed indicated by the command value X and the command value X ′, the count value Y increases, so that the difference value gradually decreases. Therefore, the CPU 7 gives a command to make the acceleration more gradual to the driver 8 than when the intermediate transfer belt 41 opened as the rotational speed of the intermediate transfer belt 41 increases.

  Further, when the rotational speed of the intermediate transfer belt 41 becomes higher than a desired speed, the count value Y increases, and the difference obtained by the CPU 7 becomes a negative value. If the integrated value becomes a negative value, for example, the CPU 7 gives an instruction to the driver 8 to stop the acceleration of the motor. Thus, when the intermediate transfer belt 41 approaches a desired speed, the belt motor 4M is intermittently turned on / off. That is, the calculation unit (CPU 7) outputs an instruction to the motor control unit (driver 8) that the motor should rotate faster as the calculated value (details will be described later) obtained by dividing the integrated value is larger. If the calculated value is negative, an instruction not to accelerate the motor is output to the motor control unit (driver 8).

  For example, when the rotational speed of the intermediate transfer belt 41 approaches a desired speed and the difference between the command value X and the count value Y becomes almost zero, the influence of the command value X ′ becomes relatively large. When the value corresponding to the command value X ′ is integrated and a carry occurs, an acceleration instruction added by the amount of the carry is given from the CPU 7 to the driver 8. As a result, the rotational speed of the intermediate transfer belt 41 can be controlled with an accuracy of a predetermined value n times the speed resolution determined by the clock signal.

  After step # 2, the CPU 7 integrates the obtained difference value and the previously calculated difference value (step # 3). Then, the CPU 7 performs a calculation for setting the integrated value to 1 / n (step # 4). Then, the CPU 7 gives an acceleration / deceleration command to the driver 8 according to the magnitude of the 1 / n value (step # 5). As a result, the belt motor 4M rotates.

  Thereafter, the CPU 7 confirms whether or not the control for rotating the intermediate transfer belt 41 may be ended by the end of printing or the like (step # 6). If it is OK (Yes in Step # 6), the CPU 7 ends this control (End). On the other hand, if control needs to be continued (No in step # 6), the process returns to step # 1.

  In this way, the rotation driving device 100 according to the present invention includes a motor (belt motor 4M and the like) for rotating the rotating body (intermediate transfer belt 41) and a motor control unit (driver 8) that controls the rotation of the motor. A speed detection unit 9 that outputs a pulse each time a driven rotating body (such as a driven roller 43a) driven by the intermediate transfer bell or the intermediate transfer belt 41 rotates by a certain angle, and a cycle T1 of a pulse generated by the speed detection unit 9. A count unit 72 that counts and counts clock signals, a value obtained by multiplying a command value (command value X, command value X ′) to be counted by the count unit 72 as a pulse period T1, by a predetermined value n, and a count Based on a calculated value obtained by calculating a difference from a value obtained by multiplying the count value Y actually counted by the unit 72 by a predetermined value n, integrating the obtained differences, and dividing the integrated value by the predetermined value n, Arithmetic unit for outputting a deceleration instruction to over motor control unit having a (CPU 7).

  In this way, the value obtained by multiplying the predetermined value n once and divided is divided by the predetermined value n. Since the value is originally less than the speed resolution, a value that is not given as the command value X, or a value that is truncated even if given (command value X ′) is multiplied by the predetermined value n. It can be given as a command value. In addition, values that were originally rounded down below the speed resolution are sequentially integrated and reflected in the acceleration / deceleration command by a carry. Accordingly, the speed resolution can be increased without increasing the clock signal speed, and the rotational speed of the motor and the rotating body (intermediate transfer belt 41, etc.) can be controlled with high accuracy. In addition, since it is not necessary to increase the clock signal speed, the manufacturing cost of the rotary drive device 100 does not increase, which is advantageous in terms of cost.

  Further, for example, when the motor rotation speed is slower than the desired rotation speed, such as at the beginning of rotating the motor, the difference between the command value and the count value becomes large. Therefore, according to this configuration, the calculation unit (CPU 7) outputs an instruction to the motor control unit (driver 8) that the motor should rotate faster as the calculated value increases. If the calculated value is a negative value, an instruction not to accelerate the motor is output to the motor control unit. Thereby, the motor and the rotating body (intermediate transfer belt 41 and the like) are maintained with high accuracy at the rotation speed at the speed according to the command value.

  The image forming apparatus (printer 200) includes a rotation driving device 100. More specifically, the image forming apparatus includes an image forming unit 3 that forms toner images of a plurality of colors, and an intermediate transfer belt 41 on which the formed toner images of the respective colors are superimposed and transferred. The speed detector 9 is attached to a roller that stretches the roller, and the speed detector 9 is a rotary encoder that is attached to the roller and outputs a pulse every time the roller rotates by a certain angle. Accordingly, since the rotation driving device 100 in which the rotation speed of the intermediate transfer belt 41 and the like is controlled with high accuracy is included, an image can be formed without deviation. Accordingly, it is possible to provide an image forming apparatus with high image quality to be formed. Further, the speed detector 9 is attached to a roller that stretches the intermediate transfer belt 41, and the rotational speed of the intermediate transfer belt 41 is controlled with high accuracy, so that the toner images can be superimposed without deviation as intended.

  The present invention also includes a motor for rotating the rotating body (intermediate transfer belt 41 and the like), a motor control unit (driver 8) for controlling the rotation of the motor, and a driven rotating body (driven by the rotating body or the rotating body). The speed detection unit 9 that outputs a pulse every time the driven roller 43a and the like rotate by a certain angle, and the counting unit 72 that counts the clock signal by counting the period T1 of the pulse generated by the speed detection unit 9 are calculated. A method of controlling the rotary drive device 100 including a calculation unit (CPU 7), wherein the calculation unit multiplies command values X and X ′ to be counted by the counting unit 72 as a pulse period T1 by a predetermined value n, A difference between a value obtained by multiplying the count value Y actually counted in 72 by a predetermined value n and a value obtained by multiplying the command values X and X ′ by the predetermined value n and a value obtained by multiplying the count value Y by the predetermined value n is obtained. Accumulated difference Based integrated value to the calculated value obtained by dividing a predetermined value n, the motor control unit can be regarded as a control method of a rotary drive apparatus 100 that outputs the deceleration command to the (driver 8).

  Next, another embodiment will be described. In the embodiment described above, an example in which the rotation driving device 100 is used for controlling the rotation speed of the intermediate transfer belt 41 has been described. However, the rotational driving device 100 of the present invention can also be used for controlling the rotational speed of other rotating bodies such as the photosensitive drum 31. For example, as the rotational speed fluctuation of the photosensitive drum 31 increases, the position of each pixel in the formed toner image shifts and affects the image quality. Therefore, a rotation driving device 100 for each photosensitive drum 31 may be provided.

  For example, as shown in FIG. 4, when the four photosensitive drums 31 are rotated by one drum motor 3M (corresponding to a motor), in the rotary drive device 100 for the photosensitive drum 31, the control unit 6 The rotation driving device 100 for the intermediate transfer belt 41 may be shared. A driver 8 that controls the rotation speed of the drum motor 3M in response to an instruction from the control unit 6 and a speed detection unit 9 for detecting the rotation speed of the photosensitive drum 31 are provided as the rotation driving device 100 for the photosensitive drum 31. That's fine. When one drum motor 3M is provided for each photosensitive drum 31, the control unit 6 may be shared, and the driver 8 and the speed detection unit 9 may be provided for each photosensitive drum 31.

  In the above embodiment, a rotary encoder is used as an example of the speed detection unit 9. However, as the speed detection unit 9, for example, a hall element provided in association with a motor may be used. What is necessary is just to emit a pulse for every fixed rotation angle according to the rotational speed of the rotating body etc. to rotate.

  The embodiment of the present invention has been described above, but the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

  The present invention can be used in a rotation driving device that rotates a rotating body such as an intermediate transfer belt, and an image forming apparatus including the rotation driving device.

3 Image forming section 31 Photosensitive drum (rotating body)
3M drum motor (motor) 4 intermediate transfer unit 41 intermediate transfer belts 43a to 43h driven roller (driven rotating body)
4M belt motor (motor) 7 CPU (calculation unit)
72 Count unit 8 Driver (motor control unit)
9 Speed Detection Unit 100 Rotation Drive Device 200 Printer (Image Forming Device) X Command Value X ′ Command Value Y Count Value

Claims (6)

A motor for rotating the rotating body;
A motor control unit for controlling rotation of the motor;
A speed detector that outputs a pulse each time the rotating body or the driven rotating body driven by the rotating body rotates by a certain angle;
A counting unit that counts the period of pulses generated by the speed detection unit by counting a clock signal;
A difference between a value obtained by multiplying a command value to be counted by the counting unit as a cycle of the pulse by a predetermined value and a value obtained by multiplying the count value actually counted by the counting unit by the predetermined value is obtained and obtained. A rotation drive device, comprising: a calculation unit that outputs an acceleration / deceleration command to the motor control unit based on a calculated value obtained by integrating the difference and dividing the integrated value by the predetermined value.   The rotary drive device according to claim 1, wherein the predetermined value is an integer.   The calculation unit outputs an instruction to the motor control unit that the motor should rotate faster as the calculated value is larger, and accelerates the motor if the calculated value is a negative value. The rotation drive device according to claim 1, wherein an instruction not to perform is output to the motor control unit.   An image forming apparatus comprising the rotation drive device according to claim 1. An image forming unit for forming a multi-color toner image;
Including an intermediate transfer belt on which the formed toner images of each color are superimposed and transferred;
A speed detector is attached to a roller that stretches the intermediate transfer belt,
The image forming apparatus according to claim 4, wherein the speed detection unit is a rotary encoder that is attached to a roller and outputs a pulse every time the roller rotates by a certain angle. A speed at which a pulse is output each time the rotating body or a driven rotating body driven by the rotating body rotates by the predetermined angle, a motor for rotating the rotating body, a motor control unit that controls the rotation of the motor, and the rotating body. A control method of a rotary drive device including a detection unit, a counting unit that counts a clock signal by counting the period of pulses generated by the speed detection unit, and a calculation unit that performs calculation,
The computing unit is
Multiplying a command value to be counted by the counting unit as a cycle of the pulse by a predetermined value,
Multiplying the count value actually counted by the count unit by the predetermined value,
A difference between a value obtained by multiplying the command value by a predetermined value and a value obtained by multiplying the count value by the predetermined value;
Accumulate the calculated differences,
A method of controlling a rotary drive device, comprising: outputting an acceleration / deceleration command to the motor control unit based on a calculated value obtained by dividing an integrated value by the predetermined value.

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